Elastomeric acetal polymers

ABSTRACT

There are provided new elastomeric copolymers of about 15 to 45 mol %, preferably about 25 to 35 mol % trioxane, about 55 to 85 mol %, preferably about 65 to 75 mol % of 1,3-dioxolane, said mol percents based on the total of trioxane and 1,3-dioxolane, and about 0.005 to 0.15 wt. %, preferably about 0.05 to 0.12 wt. % of 1,4-butanediol diglycidyl ether or butadiene diepoxide as a bifunctional monomer, based on the total weight of copolymer. The elastomeric copolymers may be prepared by mixing said monomers in a substantially dry state and under an inert atmosphere with a cationic polymerization catalyst, e.g, p-nitrobenzenediazonium tetrafluoroborate. The elastomeric copolymers have a strong interaction with moldable, crystalline acetal polymers comprising at least 85 mol % of polymerized oxymethylene units and may be used as a blending agent with such crystalline acetal polymers or as a bonding agent to improve the adhesiveness of the crystalline acetal polymer to other materials.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Molding compositions comprising acetal polymers having a high degree ofcrystallinity at room temperature have been in commercial use for manyyears. They have application in a wide variety of end uses, e.g.,automobile applications such as bumper extensions and instrument panels,plumbing supplies such as valves, shower assemblies, flush tankcomponents, faucets and pipe fittings, tool components such as screwdriver adaptors, and household and personal products, such as quickboiling electric water kettles.

These crystalline acetal polymers have a highly favorable spectrum ofphysical properties which are responsible for their wide commercialacceptance. However, for certain applications, an improved capacity ofthe latter crystalline polymers for being blended into stablehomogeneous molding compositions with other components such as certainstabilizers, would be highly desirable. Moreover, for certain end uses,e.g., those involving a laminated structure or the use of reinforcingmaterials in the interior of a molded article, a greater degree ofadhesiveness between the surface of a crystalline acetal polymer andanother surface, e.g., composed also of crystalline acetal polymer, oranother material such as glass, metal or wood, is very beneficial.

This invention relates to novel, relatively elastomeric acetalcopolymers which have little or no crystallinity at room temperature(about 25° C.). These copolymers have a strong interaction with moldableacetal polymers which contain a major proportion of oxymethylene unitsin the polymer chain and a high degree of crystallinity at roomtemperature. Because of this strong interaction, the elastomeric acetalcopolymers can be blended with moldable crystalline acetal polymers toobtain a moldable resin composition having improved morphology. Theelastomeric acetal copolymers can also be used as bonding resins betweentwo surfaces of a crystalline acetal polymer and between crystallineacetal polymers and other materials such as glass, metal or wood.

2. Description of Related Art

The following prior art references are disclosed in accordance with theterms of 37 CFR 1.56, 1.97 and 1.98.

U.S. Pat. No. 3,639,192, issued Feb. 1, 1972 to Burg et al., disclosesfor use as adhesives copolymers of formaldehyde or trioxane with 1 to60% by weight, preferably 1 to 30% by weight, of a cyclic ether cyclicand/or linear acetal, e.g., 1,3-dioxolane, and/or an alkyl glycidylformal, polyglycol diglycidyl ether or bis (alkane triol) triformal.Example 5 discloses a terpolymer of 97.95 wt.% of trioxane, 2 wt.% ofethylene oxide, and 0.05 wt.% of 1,4-butanediol diglycidyl ether.

U.S. Pat. No. 3,337,507, issued Aug. 22, 1967 to Gutweiler et al.,teaches the formation of high molecular weight copolymers obtained bypolymerizing a mixture of trioxane and any of certain polyformals.Example 4 of the patent shows the use of a polyformal which is a clearhighly viscous oil at 70° C. obtained by polymerizing a mixture of 1/3mole of trioxane and 1 mole of dioxolane in the presence ofp-nitrophenyl-diazonium fluoroborate as catalyst.

Japanese Kokai Sho 42-22065 of Yamaguchi et al., published Oct. 30,1967, discloses copolymers of trioxane and an aperiodic ring compound,e.g., 1,3-dioxolane, prepared in liquid sulfur dioxide, and in Example 1shows a copolymer of trioxane and 64 mol % of 1,3-dioxolane.

Pending application Ser. No. 096,187, filed Sept. 14, 1987 by Collins etal. and now U.S. Pat. No. 4,788,258, issued Nov. 29, 1988, discloses andclaims certain copolymers of trioxane with from 65 to 75 mol percent ofdioxolane, having an IV of about 1.0 to 2.3, which are useful asblending and adhesive agents for conventional crystalline acetalpolymers.

Pending application Ser. No. 096,189 filed Sept. 14, 1987 by Collins etal., discloses and claims bonded articles of conventional crystallineacetal polymers wherein the bonding agents are certain copolymers oftrioxane with from 65 to 75 mol percent of dioxolane, having an IV ofabout 1.0 to 2.3.

SUMMARY OF THE INVENTION

In accordance with this invention, there are provided new elastomericcopolymers of about 15 to 45 mol %, preferably about 25 to 35 mol %trioxane, about 55 to 85 mol %, preferably about 65 to 75 mol % of1,3-dioxolane, said mole percents based on the total of trioxane and1,3-dioxolane, and about 0.005 to 0.15 wt.%, preferably about 0.05 to0.12 wt.%, of 1,4-butanediol diglycidyl ether or butadiene diepoxide asa bifunctional monomer, based on the total weight of copolymer. Inaddition to being elastomeric, the copolymers of this invention aresubstantially non-crystalline at room temperature (25° C.).

Because the inventive elastomeric copolymers have a strong interactionwith normally crystalline acetal polymers widely used in the productionof various molded articles, such copolymers are effective as blendingagents for such crystalline acetal polymers, when blended with one ofthe latter polymers and any of various other components, e.g.,stabilizers. The copolymers of the invention are also effective as abonding resin between surfaces of crystalline acetal polymers andvarious other materials, e.g., another surface of a crystalline acetalpolymer, glass, metal or wood.

DESCRIPTION OF PREFERRED EMBODIMENTS

The monomers used in the preparation of the elastomeric copolymers ofthis invention are preferably fairly dry, i.e., contain no more thanabout 10 ppm of water. The monomers are dried using techniques wellknown in the art, e.g., azeotropic distillation with benzene or bydistilling the monomer in contact with sodium or potassium metal ontoactivated molecular sieves and keeping the monomer in contact withcirculating nitrogen which itself is dried by contact with P₂ O₅.

The elastomeric copolymers of this invention may be formed by a processof bulk polymerization wherein appropriate amounts of dry 1,3-dioxolaneand 1,4-butanediol diglycidyl ether (BDGE) or butadiene diepoxide areadded to dry molten trioxane to form a polymerizable mixture which inmost cases remains liquid at room temperature. The polymerizationreaction is carried out under an inert atmosphere, e.g., one obtainedusing dry nitrogen, argon, or the like, or a mixture of inert gases, inthe presence of a catalytically effective amount of a cationicpolymerization catalyst, such as p-nitrobenzenediazoniumtetrafluoroborate (PNDB), trifluoromethane sulfonic acid, borontrifluoride, a boron trifluoride etherate such as boron trifluoridedibutyletherate, or the like, e.g., an amount ranging, for example, fromabout 1 ×10⁻⁴ M/1 to about 5 ×10⁻³ M/1, and preferably from about 1×10⁻⁴ M/1 to about 1.5 ×10⁻³ M/1, based on the volume of the reactionmedium, i.e., reactants plus any solvents, suspending agents or otheradditives employed.

If PNDB is used as the catalyst, it is often convenient to add it as asolution, e.g., of about 5 to 10 wt.%, in nitromethane.

The polymerization reaction is carried out, for example, at atemperature of from about 15 to about 30° C., and preferably at fromabout 20 to about 25° C., at pressures ranging from about 750 to about770 psi, for about 15 to about 30 hours, preferably about 20 to about 25hours.

These polymers can also be prepared under the foregoing conditions bypolymerizing the monomers in a solvent, solvent mixture or suspendingagent for the monomers, e.g., a halogenated hydrocarbon such asmethylene chloride, a hydrocarbon such as hexane, cyclohexane, nonane ordodecane, or the like, or a mixture of two or more of these or othersuitable solvents or suspending agents.

In addition to the prescribed monomers, the monomer mixture used toprepare the elastomeric copolymers of this invention may contain minoramounts of related monomers, e.g., up to about 5 mol % of other cyclicformals, e.g., ethylene oxide or 1,4-butanediol formal, and up to about1 wt.% of other bifunctional monomers, e.g., diglycidyl ethers ofethylene glycol and higher alkanediols other than 1,4-butanediol.

The elastomeric copolymers of the invention will in most cases have aninherent viscosity of about 0.7 to 2.75, measured at 25° C. in a 0.2weight percent solution in hexafluoroisopropanol (HFIP). In addition,the elastomeric copolymers are in most cases substantiallynon-crystalline in the unstretched state at room temperature (25° C.),as indicated by differential scanning calorimetry (DSC) data.

The elastomeric copolymers of the invention have enhanced elastomericproperties over a wide temperature range. For example, in most casesthey can be formed into a ball that will hold its shape and will notcollapse under its own weight after an extended period. Furthermore, thecopolymers can usually be stretched in the fashion of a rubber band andsubstantially recover their previous length when released. When theelastomeric copolymers of the invention are subjected to a standardoscillatory flow test at an elevated temperature, e.g., 190° C., theyare shown to largely retain their properties of elasticity andviscosity. Thus, they are particularly suitable for being processed withmoldable crystalline acetal polymers at temperatures close to or abovethe melting points of the latter polymers for the purpose of improvingtheir morphology and/or adhesiveness to other materials.

The moldable, crystalline acetal polymers whose performance is capableof being improved by means of the elastomeric copolymers of thisinvention include any oxymethylene polymer having oxymethylene groupswhich comprise at least about 85 percent of the polymer's recurringunits, i.e., homopolymers, copolymers, terpolymers and the like.

Typically, crystalline oxymethylene homopolymers, also calledpolyformaldehydes or poly(oxymethylenes), are prepared by polymerizinganhydrous formaldehyde or trioxane, a cyclic trimer of formaldehyde. Forexample, high molecular weight polyoxymethylenes have been prepared bypolymerizing trioxane in the presence of certain fluoride catalysts,such as antimony fluoride. Polyoxymethylenes may also be prepared inhigh yields and at rapid reaction rates by the use of catalystscomprising boron fluoride coordination complexes with organic compounds,as described in Hudgin et al. U.S. Pat. No. 2,898,506.

Oxymethylene homopolymers are usually stabilized against thermaldegradation by end-capping with, for example, ester or ether groups suchas those derived from alkanoic anhydrides, e.g., acetic anhydride, ordialkyl ethers, e.g., dimethyl ether, or by incorporating stabilizercompounds into the homopolymer, as described in Dolce et al. U.S. Pat.No. 3,133,896.

Crystalline oxymethylene copolymers which are especially suitable forutilization with the elastomeric copolymers of this invention willusually possess a relatively high level of polymer crystallinity, i.e.,about 60 to 80 percent or higher. These preferred oxymethylenecopolymers have repeating units which consist essentially ofoxymethylene groups interspersed with oxy(higher)alkylene groupsrepresented by the general formula: ##STR1## wherein each R₁ and R₂ ishydrogen or a lower alkyl group, each R₃ is a methylene, oxymethylene,lower alkyl-substituted methylene or lower alkyl-substitutedoxymethylene group, and n is an integer from zero to three, inclusive.Each lower alkyl group preferably contains one or two carbon atoms.

Oxymethylene groups generally will constitute from about 85 to about99.9 percent of the recurring units in such crystalline copolymers. Theoxy(higher)alkylene groups incorporated into the copolymer duringcopolymerization produce the copolymer by the opening of the ring of acyclic ether or cyclic formal having at least two adjacent carbon atoms,i.e., by the breaking of an oxygen-to-carbon linkage.

Crystalline copolymers of the desired structure may be prepared bypolymerizing trioxane together with from about 0.1 to about 15 molpercent of a cyclic ether or cyclic formal having at least two adjacentcarbon atoms, preferably in the presence of a catalyst such as a Lewisacid (e.g., BF₃, PF₅, and the like) or other acids (e.g., HClO₄, 1% H₂SO₄, and the like), ion pair catalysts, etc.

In general, the cyclic ethers and cyclic formals employed in makingthese preferred crystalline oxymethylene copolymers are thoserepresented by the general formula: ##STR2## wherein each R₁ and R₂ ishydrogen or a lower alkyl group, each R₃ is a methylene, oxymethylene,lower alkyl-substituted methylene or lower alkyl-substitutedoxymethylene group, and n is an integer from zero to three, inclusive.Each lower alkyl group preferably contains one or two carbon atoms.

The cyclic ether and cyclic formal preferred for use in preparing thesepreferred crystalline oxymethylene copolymers are ethylene oxide and1,3-dioxolane, respectively. Among the other cyclic ethers and cyclicformals that may be employed are 1,3-dioxane, trimethylene oxide,1,2-propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide,1,4-butanediol formal, and the like.

Crystalline oxymethylene copolymers produced from the preferred cyclicethers have a structure composed substantially of oxymethylene andoxy(lower)alkylene, preferably oxyethylene, groups, and arethermoplastic materials having a melting point of at least 150° C. Theynormally are millable or processable at temperatures ranging from 180°C. to about 200° C., and have a number average molecular weight of atleast 10,000 and an inherent viscosity of at least 1.0 (measured atabout 25° C. in a 0.2 weight percent solution in HFIP).

These crystalline oxymethylene copolymers preferably are stabilized to asubstantial degree prior to being utilized with the elastomericcopolymers of this invention. This can be accomplished by degradation ofunstable molecular ends of the polymer chains to a point where arelatively stable carbon-to-carbon linkage exists at each end of eachchain. Such degradation may be effected by hydrolysis, as disclosed, forexample, Berardinelle in U.S. Pat. No. 3,219,623.

The crystalline oxymethylene copolymer may also be stabilized byend-capping, again using techniques well known to those skilled in theart. End-capping is preferably accomplished by acetylation with aceticanhydride in the presence of sodium acetate catalyst.

A particularly preferred class of crystalline oxymethylene copolymers iscommercially available from Hoechst-Celanese Corporation under thedesignation CELCON acetal copolymer, and especially preferred is CELCONM25 acetal copolymer, which has a melt index of about 2.5g/10 min. whentested in accordance with ASTM D1238-82.

Crystalline oxymethylene terpolymers having oxymethylene groups,oxy(higher)alkylene groups such as those corresponding to theabove-recited general formula: ##STR3## and a different, third groupinterpolymerizable with oxymethylene and oxy(higher)alkylene groups maybe prepared, for example, by reacting trioxane, a cyclic ether or cyclicacetal and, as the third monomer, a bifunctional compound such asdiglycide of the formula: ##STR4## wherein Z represents acarbon-to-carbon bond, an oxygen atom, an oxyalkoxy group of 1 to 8carbon atoms, inclusive, preferably 2 to 4 carbon atoms, anoxycycloalkoxy group of 4 to 8 carbon atoms, inclusive, or anoxypoly(lower alkoxy)group, preferably one having from 2 to 4 recurringlower alkoxy groups each with 1 or 2 carbon atoms, for example, ethylenediglycide, diglycidyl ether and diethers of 2 mols of glycide and 1 molof an aliphatic diol with 2 to 8 carbon atoms, advantageously 2 to 4carbon atoms, or a cycloaliphatic diol with 4 to 8 carbon atoms.

Examples of suitable bifunctional compounds include the diglycidylethers of ethylene glycol; 1,4-butanediol; 1,3-butanediol;cyclobutane-1,3-diol; 1,2-propanediol; cyclohexane-1,4-diol and2,2,4,4-tetramethylcyclobutane-1,3-diol, with butanediol diglycidylethers being most preferred.

Generally, when preparing such crystalline terpolymers, ratios of from99.89 to 89.0 weight percent trioxane, 0.1 to 10 weight percent of thecyclic ether or cyclic acetal and 0.01 to 1 weight percent of thebifunctional compound are preferred, these percentages being based onthe total weight of monomers used in forming the terpolymer. Ratios offrom 99.85 to 89.5 weight percent of trioxane, 0.1 to 10 weight percentof cyclic ether or cyclic acetal and 0.05 to 0.5 weight percent ofdiglycidyl ether are particularly preferred, these percentages againbeing based on the total weight of monomers used in forming theterpolymer.

Terpolymer polymerization in preparing the contemplated crystallineterpolymers may be carried out according to known methods of solid,solution or suspension polymerization. As solvents or suspending agents,one may use inert aliphatic or aromatic hydrocarbons, halogenatedhydrocarbons or ethers.

Trioxane-based terpolymer polymerization is advantageously carried outat temperatures at which trioxane does not crystallize out, that is, attemperatures within the range of from about 65° C. to about 100° C.

Cationic polymerization catalysts, such as organic or inorganic acids,acid halides and, preferably, Lewis acids, can be used in preparing thecrystalline terpolymers. Of the latter, boron fluoride and its complexcompounds, for example, etherates of boron fluoride, are advantageouslyused. Diazonium fluoroborates are particularly advantageous.

Catalyst concentration may be varied within wide limits, depending onthe nature of the catalyst and the intended molecular weight of thecrystalline terpolymer. Thus, catalyst concentration may range fromabout 0.0001 to about 1 weight percent, and preferably will range fromabout 0.001 to about 0.1 weight percent, based on the total weight ofthe monomer mixture.

Since catalysts tend to decompose the crystalline terpolymer, thecatalyst is advantageously neutralized immediately after polymerizationusing, for example, ammonia or methanolic or acetonic amine solutions.

Unstable terminal hemiacetal groups may be removed from the crystallineterpolymers in the same manner as they are from other oxymethylenepolymers. Advantageously, the terpolymer is suspended in aqueous ammoniaat temperatures within the range of from about 100° C. to about 200° C.,if desired in the presence of a swelling agent such as methanol orn-propanol. Alternatively, the terpolymer is dissolved in an alkalinemedium at temperatures above 100° C. and subsequently reprecipitated.Suitable alkaline media include benzyl alcohol, ethylene glycolmonoethyl ether, or a mixture of 60 weight percent methanol and 40weight percent water containing ammonia or an aliphatic amine.

The crystalline terpolymers may also be thermally stabilized bydegrading unstable molecular ends of their chains to a point where arelatively stable carbon-to-carbon linkage exists at each end of eachchain. Thermal stabilization will preferably be carried out in theabsence of a solvent in the melt, in the presence of a thermalstabilizer.

Alternatively, the crystalline terpolymer can be subjected toheterogeneous hydrolysis wherein water, with or without a catalyst,e.g., an aliphatic or aromatic amine, is added to a melt of theterpolymer in an amount ranging from about 1 to about 50 percent byweight, based on the weight of the terpolymer. The resulting mixture ismaintained at a temperature in the range of from about 170° C. to 250°for a specified period of time, and then washed with water and dried orcentrifuged.

A preferred crystalline oxymethylene terpolymer is commerciallyavailable from Hoechst-Celanese Corporation under the designation CELCONU10 acetal polymer, and is a butanediol diglycidyl ether/ethyleneoxide/trioxane terpolymer containing about 0.05 weight percent, 2.0weight percent, and 97.95 weight percent of repeating units derived fromthese termonomers, respectively, based on the total weight of thesetermonomers.

Crystalline oxymethylene polymers admixed with plasticizers,formaldehyde scavengers, mold lubricants, antioxidants, fillers,colorants, reinforcing agents, light stabilizers and other stabilizers,pigments, and the like, can be used with the elastomeric copolymers ofthis invention so long as such additives do not materially affect thedesired interaction between the crystalline polymer and the elastomericcopolymer, particularly enhancement of impact strength of blends of thetwo polymers. Such additives can be admixed with the elastomericcopolymer of this invention, the crystalline oxymethylene polymer, orthe blend of two using conventional mixing techniques.

Suitable formaldehyde scavengers include cyanoguanidine, melamine andmelamine derivatives, such as lower alkyl- and amine-substitutedtriazines, amidines, polyamides, ureas, metal oxides and hydroxides,such as calcium hydroxide, magnesium hydroxide, and the like, salts ofcarboxylic acids, and the like. Cyanoguanidine is the preferredformaldehyde scavenger. Suitable mold lubricants include alkylenebisstearamides, long-chain amides, waxes, oils, and polyether glycides.A preferred mold lubricant is commercially available from GlycolChemical, Inc. under the designation Acrawax C, and is an alkylenebisstearamide. The preferred antioxidants are hindered bisphenols.Especially preferred is 1,6-hexamethylenebis-(3,5-di-t-butyl-hydroxyhydrocinnamate), commercially available fromCiba-Geigy Corp. under the designation Irganox 259.

A most preferred crystalline oxymethylene two component copolymer foruse with the elastomeric copolymers of this invention is commerciallyavailable from Hoechst Celanese Corporation under the designation CELCONM25-04 acetal polymer. This is the previously mentioned CELCON M25acetal copolymer stabilized by 0.5 percent by weight Irganox 259, 0.1percent by weight cyanoguanidine, and 0.2 percent by weight Acrawax C.

A most preferred crystalline oxymethylene terpolymer for use with theelastomeric copolymers of this invention is commercially available fromHoechst Celanese Corporation under the designation CELCON U10-11 acetalpolymer. This is the previously mentioned CELCON U-10 acetal terpolymerstabilized by 0.5 percent by weight Irganox 259 and 0.1 percent byweight calcium ricinoleate.

The following examples further illustrate the invention.

EXAMPLE 1

Dry, freshly distilled, molten trioxane in an amount of 300 ml wastransferred under a nitrogen atmosphere to a half gallon reactor fittedwith a magnetic stirrer which was previously purged with nitrogen. Therewere then added to the reactor under a nitrogen atmosphere 700 ml of dry1,3-dioxolane and 1 ml of dry 1,4-butanediol diglycidyl ether (BDGE).The mixture was allowed to fall to room temperature (25° C.). Thecatalyst for the reaction was p-nitrobenzenediazonium tetrafluoroborate(PNDB) which was initially added as 3 ml of a dry solution of 356 mg in10 ml of nitromethane (0.45 ×10⁻³ M/1 of catalyst). Before reactionstarted, 1 ml of the reaction mass was tested in a moisture meter andfound to contain no water. Subsequently, an additional amount of PNDB as2 ml of a solution of 1186 mg of the catalyst in 10 ml of nitromethane(1 1 ×10⁻³ M/1 of catalyst) was added to the reactor.

After about 24 hours of polymerization, the stirrer was stopped and 700ml of methylene chloride plus enough tributylamine to neutralize thecatalyst were added and the reaction shaken for about 24 hours, afterwhich some of the polymer remained undissolved. The solution was thenremoved from the reactor.

An additional 500 ml of methylene chloride were added to the undissolvedpolymer and the material shaken for 24 hours, after which some of thepolymer still remained undissolved. The solution was removed and addedto 1000 ml of cold ethanol and stirred with a mechanical shaft stirrerfor 1-2 hours. The resulting two-phase mixture was placed in an ice bathand allowed to stand for two hours after which time solid polymersettled. The ethanol was decanted and the polymer dried in a vacuumoven. The polymer was found by NMR analysis to contain about 32.0 mol %of polymerized trioxane and about 68.0 mol % of polymerized1,3-dioxolane. It had an inherent viscosity (IV) of 2.46.

The work-up procedure described in the previous paragraph was repeatedwith the undissolved polymer remaining in the polymerization reactor.This polymer had an IV of 2.48.

EXAMPLE 2

The polymerization and work-up procedures of Example 1 weresubstantially followed except that only 2 ml of a solution of 1186 mg ofPNDB in 10 ml of nitromethane (1 ×10⁻³ M/1 of catalyst) was added toinitiate the reaction. Before initiation, 1 ml of the solution wastested in a moisture meter and found to contain no water.

Three cuts of polymer were taken by agitating with methylene chloride.The first cut obtained by agitating with 700 ml of methylene chloridefor about 2 days had an IV of 2.70. The second cut obtained by agitatingthe undissolved polymer with 500 ml of methylene chloride for about 2days was found by NMR analysis to contain 28.0 mol % of polymerizedtrioxane and 72.0 mol % of polymerized 1,3-dioxolane and had an IV of2.26. The third cut obtained by agitating the still undissolved polymerwith an additional 500 ml of methylene chloride had an IV of 2.07.

EXAMPLE 3

The polymerization and work-up procedures of Example 2 weresubstantially followed. Before initiation of the reaction, 1 ml of thesolution was found to contain no water. The first cut of polymer had anIV of 2.16. The second cut contained 26.0 mol % of polymerized trioxaneand 74.0 mol % of polymerized 1,3-dioxolane and had an IV of 1.89. Thethird cut had an IV of 0.84.

EXAMPLE 4

The polymerization and work-up procedures of Example 2 weresubstantially followed. The first cut of polymer had an IV of 1.68. Thesecond cut contained 30.0 mol % of polymerized trioxane and 70.0 mol %of polymerized 1,3-dioxolane and had an IV of 1.39. The third cut had anIV of 0.82.

Polymers similar in properties to those of the foregoing examples can beobtained by substituting butadiene diepoxide for the 1,4-butanedioldiglycidyl ether in approximately the same amount by weight.

The polymers of the foregoing examples are useful as blending agents forthe moldable crystalline acetal polymers as described previously and asbonding agents for the purpose of increasing the adhesiveness of suchcrystalline acetal polymers to other materials such as other surfaces ofthe same crystalline polymer, and glass.

We claim:
 1. An elastomeric copolymer of about 15 to 45 mol % oftrioxane and about 55 to 85 mol % of 1,3-dioxolane based on the total oftrioxane and 1,3-dioxolane, and about 0.005 to 0.15 wt.% of1,4-butanediol diglycidyl ether or butadiene diepoxide as a bifunctionalmonome, based on the total weight of copolymer, said copolymer beingsubstantially non-crystalline in the unstretched state at roomtemperature.
 2. The elastomeric copolymer of claim 1 containing about 25to 35 mol % of trioxane and about 65 to 75 mol % of 1,3-dioxolane basedon the total of trioxane and 1,3-dioxolane, and about 0.05 to 0.12 wt.%of 1,4-butanediol diglycidyl ether or butadiene diepoxide as abifunctional monomer, based on the total weight of copolymer.
 3. Theelastomeric copolymer of claim 1 containing 1,4-butanediol diglycidylether as bifunctional monomer.
 4. The elastomeric copolymer of claim 1containing butadiene diepoxide as bifunctional monomer.
 5. Theelastomeric copolymer of claim 1 having an inherent viscosity of about0.7 to 2.75 measured at about 25° C. in a 0.2 weight percent solution inhexafluoroisopropanol.